“It’s really tough when you play one Williams,” Venus said. “When you play two, it’s really not an easy win.”

The sisters will be ranked No. 1 in doubles for the first time next week in a partnership that began in the 1980s. They laughed as they reminisced about learning to play doubles.

“My dad told Venus to cross more, and so I think she got upset, and she crossed when the person was serving,” Serena said. “Dad told me I had to play the forehand, because I was young and I was smaller, and then he put Venus on the backhand. It has been like that ever since. That was 20 years ago?”

“At least,” Venus said.

It’s the siblings’ second French Open doubles championship, with the other coming in 1999. For several years they played little doubles, but they plan to keep playing together at the major tournaments.

“We just realize what it’s like to have that major title next to your name, and it’s pretty addictive,” Venus said.

“When you’re out there and you’re playing singles, it’s a great feeling obviously,” Serena said. “But also to play doubles with someone that’s your sister, your flesh and blood, that’s even better.”

The victory compensated at least somewhat for the sisters’ disappointment in singles. No. 1-ranked Serena lost in the quarterfinals, and No. 2 Venus lost in the fourth round.